WO2019153619A1

WO2019153619A1 - Sulfur and nitrogen co-doped graphene-based aerogel and preparation method therefor

Info

Publication number: WO2019153619A1
Application number: PCT/CN2018/091547
Authority: WO
Inventors: 慈立杰; 任小花; 郭焕焕
Original assignee: 山东大学
Priority date: 2018-02-07
Filing date: 2018-06-15
Publication date: 2019-08-15
Also published as: CN108439372B; CN108439372A

Abstract

Disclosed are a sulfur and nitrogen co-doped graphene-based aerogel and a preparation method therefor. A sulfur and nitrogen co-doped graphene hydrogel precursor is prepared by using graphene oxide and thiourea as raw materials and by means of a hydrothermal synthesis method. The resulting precursor is subjected to vacuum freeze-drying and then to carbonization so as to obtain the sulfur and nitrogen co-doped graphene-based aerogel. The sulfur and nitrogen co-doped graphene aerogel prepared by the method has an ultra-hydrophobic property and a lipophilic property, a good mechanical property, and a high oil and organic solvent absorption rate. In addition, the preparation method is simple, the sources of the raw materials thereof are extensive, and the method is green and environmentally friendly.

Description

Sulfur-nitrogen co-doped graphene-based aerogel and preparation method thereof

Technical field

The invention belongs to the field of carbon nano material and oil-water separation, and relates to a superhydrophobic high oil absorption performance sulfur-nitrogen co-doped graphene-based aerogel and a preparation method thereof.

Background technique

Leakage of marine oil spills, industrial oily wastewater and organic solvents pose serious risks to aquatic ecosystems and human health, and there is an urgent need to develop new materials and technologies that can efficiently clean such pollution from the surface of the water. At present, commonly used materials and technologies mainly include chemical curing method, in-situ combustion method, bioremediation method, and mechanical repair method (adsorbent and skimmer), in which the adsorbent adsorption method has complete in-situ removal. The potential of oil slicks has received much attention without adversely affecting the ecosystem.

As a good oil absorbing material, it should have the characteristics of hydrophobicity and lipophilicity, high oil absorption capacity, low cost and stable floating on the water surface. However, conventional oil slag adsorbents face problems such as low oil/water separation efficiency, low oil absorption capacity, and high material cost. Carbon-based ultra-light adsorption materials (such as graphene and carbon nanotube aerogel) have the characteristics of hydrophobic/lipophilic, porous, low density and chemical stability, and have a good application prospect in oil absorbing. Among them, graphene is an excellent material for constructing multifunctional, high-performance macroscopic three-dimensional aerogels. As one of the most attractive carbon materials, graphene aerogel has unique properties such as ultra-low density, superelasticity, high specific surface area and excellent thermal stability, making them energy storage, pressure sensors, pollutant adsorption, etc. Aspects show great potential. However, an aerogel assembled by simply using graphene oxide as a precursor is easily agglomerated, has low mechanical strength, and is poor in hydrophobicity.

Chinese patent (CN 102874796 A) provides a nitrogen-doped graphene hydrogel or aerogel and a preparation method thereof, the main steps include: ultrasonically oxidizing graphite to form a graphene oxide dispersion; then adding a nitrogen source to prepare nitrogen by self-assembly Doped graphene hydrogel; finally dried to obtain a nitrogen-doped graphene aerogel. The nitrogen-doped graphene aerogel prepared by the method has a rough surface and agglomerates, and has low mechanical strength.

The Chinese patent (CN 106006616 A) provides a method for preparing a graphene aerogel with high adsorption performance, as long as the steps include: adding graphene oxide to deionized water, ultrasonically preparing an aqueous solution of graphene oxide; adding an aqueous solution of ammonia borane And the aqueous solution of ferrous sulfate is uniformly mixed; then the graphene hydrogel is prepared by constant temperature hydrothermal reaction; finally, the immersion, pre-freezing and freeze-drying are used to obtain a graphene aerogel with high adsorption performance. The graphene aerogel prepared by the method has large pore size, small specific surface area and low adsorption efficiency; in addition, the metal ions contained in the raw material cause secondary heavy metal pollution to the water body.

Summary of the invention

In order to solve the deficiencies of the prior art, one of the objects of the present invention is to provide a method for preparing a sulfur-nitrogen co-doped graphene-based aerogel. The sulfur-nitrogen co-doped graphene aerogel prepared by the method has superhydrophobicity. Performance and lipophilic properties, good mechanical properties, high oil absorption and organic solvent ratio. In addition, the preparation method is simple, the raw materials are widely sourced, and the environment is green. The sulfur-nitrogen co-doped graphene aerogel has a good application prospect in oil spill accidents and organic solvent leakage treatment.

In order to achieve the above object, the technical solution of the present invention is:

A preparation method of sulfur-nitrogen co-doped graphene-based aerogel, preparing a sulfur-nitrogen co-doped graphene hydrogel precursor by hydrothermal reaction method using graphene oxide and thiourea as raw materials, and obtaining precursors A sulfur-nitrogen co-doped graphene-based aerogel can be obtained by performing carbonization after vacuum freeze-drying.

The invention realizes simultaneous doping of nitrogen and sulfur into the graphene aerogel by adding thiourea, and the incorporation of sulfur not only enhances the hydrophobic property of the graphene-based aerogel, but also increases the mechanical strength thereof. The invention adopts sulfur-nitrogen co-doped graphene aerogel as adsorbent for adsorption of oil and organic solvent, has high adsorption capacity and good recycling performance. The invention does not need the addition of metal elements, avoids causing metal pollution of water bodies, and is environmentally friendly.

Another object of the present invention is to provide a sulfur-nitrogen co-doped graphene-based aerogel obtained by the above production method.

A third object of the present invention is to provide an application of the above sulfur-nitrogen co-doped graphene-based aerogel in oil-water separation.

The invention has the beneficial effects that the prepared sulfur-nitrogen co-doped graphene aerogel has superhydrophobic property, the water contact angle is greater than 150°, and has high lipophilicity, and the oil contact angle is less than 10°; the graphene-based aerogel It has high oil absorption and organic solvent ratio, about 65-190g/g; the graphene-based aerogel has good compression performance, maintains three-dimensional porous structure after 1000 times of compression, and has good recycling performance; The doped graphene-based aerogel has simple preparation method, wide source of raw materials, low price, high adsorption capacity and good recycling performance, and has good application prospects in oil spill accidents and organic solvent leakage treatment.

DRAWINGS

The accompanying drawings, which are incorporated in the claims of the claims

1 is a scanning electron microscope (SEM) image of a sulfur-nitrogen co-doped graphene aerogel;

2 is a water and oil contact angle diagram of the prepared sulfur-nitrogen co-doped graphene aerogel;

3 is an X-ray photoelectron spectroscopy (XPS) diagram of the prepared sulfur-nitrogen co-doped graphene aerogel;

4 is a N ₂ adsorption-desorption diagram of the prepared sulfur-nitrogen co-doped graphene aerogel;

Figure 5 is a stress-strain diagram of the prepared sulfur-nitrogen co-doped graphene aerogel;

6 is an SEM image of the prepared sulfur-nitrogen co-doped graphene aerogel after 1000 compressions;

7 is a diagram showing adsorption of oil and organic solvents by a sulfur-nitrogen co-doped graphene aerogel;

Figure 8 is a diagram showing the adsorption of pump oil and ethanol after the sulfur-nitrogen co-doped graphene aerogel is compressed 1000 times;

Figure 9 is a cyclic adsorption performance of the prepared sulfur-nitrogen co-doped graphene aerogel.

Detailed ways

It should be noted that the following detailed description is exemplary and is intended to provide a further description of the application. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise indicated.

It is to be noted that the terminology used herein is for the purpose of describing particular embodiments, and is not intended to limit the exemplary embodiments. As used herein, the singular " " " " " " There are features, steps, operations, devices, components, and/or combinations thereof.

The hydrothermal reaction described in the present application refers to a reaction carried out under high temperature and high pressure in a sealed pressure vessel using water as a solvent. The high temperature refers to 100 to 1000 ° C, and the high pressure refers to 1 MPa to 1 GPa.

Carbonization as used herein refers to the process of thermal decomposition under anoxic conditions.

As described in the background art, in the prior art, there is a problem that the graphene aerogel is easy to agglomerate, the mechanical strength is low, and the hydrophobicity is poor. In order to solve the above technical problem, the present application proposes a sulfur-nitrogen co-doped graphite. Alkenyl aerogel and preparation method thereof.

An exemplary embodiment of the present application provides a method for preparing a sulfur-nitrogen co-doped graphene-based aerogel, which comprises preparing a sulfur-nitrogen co-doped graphene by hydrothermal synthesis using graphene oxide and thiourea as raw materials. The hydrogel precursor is obtained by subjecting the obtained precursor to vacuum freeze-drying and then carbonizing to obtain a sulfur-nitrogen co-doped graphene-based aerogel.

The present application achieves simultaneous doping of nitrogen and sulfur into the graphene aerogel by adding thiourea. The incorporation of sulfur not only enhances the hydrophobic properties of the graphene alkane, but also increases its mechanical strength. In the present application, the sulfur-nitrogen co-doped graphene aerogel is used as an adsorbent for the adsorption of oils and organic solvents, and has high adsorption capacity and good recycling performance. This application does not require the addition of metal elements to avoid causing metal pollution in water bodies and is environmentally friendly.

Preferably, the hydrothermal reaction conditions are: a temperature of 160 to 200 ° C, and a reaction time of 8 to 12 h. The volume ratio of the material volume to the volume of the reactor is 3 to 4:5.

Preferably, the conditions of vacuum freeze-drying are: a temperature of -80 to -60 ° C, and a time of 48 to 72 h.

Preferably, the carbonization process is: the lyophilized precursor is heated to 600-800 ° C for 0.5 to 2 h under an inert gas atmosphere.

Preferably, the mass ratio of thiourea to graphene oxide is from 10 to 50:1.

Preferably, the thiourea is added to the aqueous graphene oxide solution and mixed uniformly, followed by a hydrothermal reaction.

More preferably, the concentration of graphene oxide in the aqueous graphene oxide solution is 2 to 4 mg/mL. In order to accelerate the mixing rate, ultrasonic vibration assisted mixing was employed in the preparation of the aqueous graphene oxide solution and the addition of thiourea to the aqueous graphene oxide solution for mixing.

In order to remove the free thiourea, it is preferred to soak in water for a period of time after the hydrothermal reaction. Further preferably, the soaking time is 48 to 72 hours.

Preferably, pre-freezing is carried out at -60 to -20 °C before vacuum drying. The pre-freezing time is 2 to 6 hours.

In another embodiment of the present application, a sulfur-nitrogen co-doped graphene-based aerogel obtained by the above preparation method is provided.

A third embodiment of the present application provides the use of the above sulfur-nitrogen co-doped graphene-based aerogel in oil-water separation. Preferably, the oil is carbon tetrachloride.

In order to enable those skilled in the art to understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

The graphene oxide in the present application may be a commercially available graphene oxide, or may be prepared according to a preparation method of other literatures. The present application provides a method for preparing graphene oxide, the steps of which are:

Under ice bath at 0 ° C, 18 g of potassium permanganate and 3 g of sodium nitrate were slowly added to 138 mL of concentrated sulfuric acid while mechanically stirring at a rate of 200-500 rpm. After the potassium permanganate and sodium nitrate were completely dissolved, slowly Add 3g of expanded graphite, after the expanded graphite is completely stirred, seal it in the refrigerator and keep it at 0 °C for 24h; then transfer the reaction system to a 35 °C constant temperature oil bath, stir the reaction for 30min, then slowly add deionization while heating. Water, add a total of 300mL of deionized water, the temperature just rises to 98 ° C, stir at 98 ° C for 15 min, then use 10 ~ 15mL of 30% hydrogen peroxide and the remaining oxidant, the mixture changes from black to gold Yellow; washed 3 to 5 times with 5% hydrochloric acid, and then thoroughly washed with deionized water until the pH is 6-8, and then centrifuged at 8000 rpm to freeze-dry the final product to obtain graphene oxide.

Example 1

Method for preparing sulfur-nitrogen co-doped graphene-based aerogel,

(1) 80 mg of graphene oxide was added to 40 mL of deionized water, and ultrasonically dispersed for 1 hour until homogeneously mixed to obtain a 2 mg/mL aqueous graphene oxide solution.

(2) 1.6 g of thiourea was weighed as a source of sulfur nitrogen, which was mixed with the aqueous graphene oxide solution obtained in the step (1), and completely dissolved by ultrasonication for 15 minutes to obtain a mixed aqueous solution of graphene oxide and thiourea.

(3) The mixed aqueous solution obtained in the step (2) is transferred to a high-pressure reaction vessel having a volume of 50 mL, and hydrothermally reacted at 160 ° C for 12 hours, and then naturally cooled to obtain a sulfur-nitrogen co-doped graphene hydrogel precursor. body.

(4) The sulfur-nitrogen co-doped graphene hydrogel precursor prepared in the step (3) was immersed in deionized water for 48 hours, and the deionized water was replaced three times.

(5) The hydrogel after the step (4) is pre-frozen at -20 ° C for 6 h, and then vacuum-dried at -80 ° C for 48 h to obtain a sulfur-nitrogen co-doped graphene gas-condensation after freeze-drying. Glue precursor.

(6) The freeze-dried sulfur-nitrogen co-doped graphene aerogel precursor obtained in the step (5) is carbonized at 600 ° C for 2 h under an argon atmosphere to obtain a superhydrophobic high oil absorption performance sulfur-nitrogen co-doping. Graphene aerogel.

The aerogel prepared in this example was characterized, and the results of the characterization are shown in Figures 1-9.

Figure 1 shows that the prepared sulfur-nitroco-doped graphene aerogel has a continuous porous three-dimensional structure.

Figure 2 shows that the prepared sulfur-nitrogen co-doped graphene aerogel has superhydrophobic properties (a) and lipophilic properties (b), and it can be seen that the water contact angle of the sulfur-nitrogen co-doped graphene aerogel is 151.5°. The oil contact angle is 9.5°.

The characterization results in Figure 3 indicate that the prepared sulfur-nitroco-doped graphene aerogel contains C, S, N and O elements.

The results of the characterization of Figure 4 indicate that the prepared sulfur-nitrogen co-doped graphene aerogel has a large BET comparison area of 406.80 m ² /g.

The characterization results in Figure 5 indicate that the prepared sulfur-nitrogen co-doped graphene aerogel has good mechanical properties and compression-recovery properties, and can quickly return to the initial state at 90% compression.

Figure 6 is an SEM image after 1000 compressions. It can be seen that the sulfur-nitrogen co-doped graphene aerogel still maintains a good three-dimensional porous structure after 1000 compressions.

The adsorption of sulfur-nitrogen co-doped graphene aerogel prepared in Figure 7 on oils and organic solvents shows that it has good adsorption properties for various oils and organic solvents, especially for tetrachloroethylene. Carbon adsorption has the best effect.

Figure 8 is a diagram showing the adsorption of pump oil and ethanol after 1000 times of sulfur-nitrogen co-doped graphene aerogel. The results show that the sulfur-nitrogen co-doped graphene aerogel still has good after 1000 compressions. Adsorption capacity.

Figure 9 is a cyclic adsorption diagram of sulfur-nitrogen co-doped graphene aerogel on pump oil and ethanol. The point of about 400-500 mg (the upper two rows in the figure) represents the total mass of the aerogel adsorption pump oil or ethanol. The dots of about 0 to 30 mg (the lower two rows in the figure) represent the initial mass of the aerogel and the mass after compression and removal of the organic solvent. It shows that the prepared sulfur-nitrogen co-doped graphene aerogel has good recycling performance.

Example 2

Method for preparing sulfur-nitrogen co-doped graphene-based aerogel,

(1) 120 mg of graphene oxide was added to 40 mL of deionized water, and ultrasonically dispersed for 2 hours until homogeneously mixed to obtain a 3 mg/mL aqueous graphene oxide solution.

(2) 3.6 g of thiourea was weighed as a source of sulfur nitrogen, which was mixed with the aqueous graphene oxide solution obtained in the step (1), and completely dissolved by ultrasonication for 20 minutes to obtain a mixed aqueous solution of graphene oxide and thiourea.

(3) The mixed aqueous solution obtained in the step (2) is transferred to a high-pressure reaction vessel having a volume of 50 mL, and hydrothermally reacted at 200 ° C for 8 hours, and after natural cooling, a sulfur-nitrogen co-doped graphene hydrogel precursor is obtained. body.

(4) The sulfur-nitrogen co-doped graphene hydrogel precursor prepared in the step (3) was immersed in deionized water for 72 hours, during which time deionized water was replaced five times.

(5) The hydrogel after the step (4) is pre-frozen at -60 ° C for 2 h, and then vacuum-dried at -80 ° C for 72 h to obtain a sulfur-nitrogen co-doped graphene gas-condensation after freeze-drying. Glue precursor.

(6) The freeze-dried sulfur-nitrogen co-doped graphene aerogel precursor obtained in the step (5) is carbonized at 800 ° C for 0.5 h under an argon atmosphere to obtain a superhydrophobic high oil absorption sulfur-nitrogen co-doping. A heterographene aerogel.

Example 3

Method for preparing sulfur-nitrogen co-doped graphene-based aerogel,

(1) 160 mg of graphene oxide was added to 40 mL of deionized water, and ultrasonically dispersed for 1.5 hours until homogeneously mixed to obtain 4 mg/mL of an aqueous graphene oxide solution.

(3) The mixed aqueous solution obtained in the step (2) is transferred to a high-pressure reaction vessel having a volume of 50 mL, and hydrothermally reacted at 180 ° C for 10 hours, and after natural cooling, a sulfur-nitrogen co-doped graphene hydrogel precursor is obtained. body.

(4) The sulfur-nitrogen co-doped graphene hydrogel precursor prepared in the step (3) was immersed in deionized water for 60 hours, and the deionized water was replaced 4 times.

(5) The hydrogel after the step (4) is pre-frozen at -40 ° C for 4 h, and then vacuum-dried at -80 ° C for 48 h to obtain a sulfur-nitrogen co-doped graphene gas condensate after freeze-drying. Glue precursor.

(6) The freeze-dried sulfur-nitrogen co-doped graphene aerogel precursor obtained in the step (5) is carbonized at 700 ° C for 1 h under an argon atmosphere to obtain a superhydrophobic high oil absorption sulfur-nitrogen co-doping. Graphene aerogel.

The characterization results of Examples 2 to 3 were the same as in Example 1.

The above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and various changes and modifications may be made to the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application are intended to be included within the scope of the present application.

Claims

A preparation method of sulfur-nitrogen co-doped graphene-based aerogel, characterized in that a sulfur-nitrogen co-doped graphene hydrogel precursor is prepared by hydrothermal synthesis using graphene oxide and thiourea as raw materials, The obtained precursor is subjected to vacuum freeze-drying and then carbonized to obtain a sulfur-nitrogen co-doped graphene-based aerogel.
The preparation method according to claim 1, wherein the hydrothermal reaction conditions are: a temperature of 160 to 200 ° C, and a reaction time of 8 to 12 h.
The preparation method according to claim 1, wherein the vacuum freeze-drying conditions are: a temperature of -60 to -80 ° C and a time of 48 to 72 hours.
The preparation method according to claim 1, wherein the carbonization process is: the lyophilized precursor is heated to 600 to 800 ° C for 0.5 to 2 hours under an inert gas atmosphere.
The process according to claim 1, wherein the mass ratio of thiourea to graphene oxide is from 10 to 50:1.
The process according to claim 1, wherein the thiourea is added to the aqueous graphene oxide solution and uniformly mixed, followed by a hydrothermal reaction.
The preparation method according to claim 1, wherein the hydrothermal reaction is carried out for a while in water. Further preferably, the soaking time is 48 to 72 hours.
The process according to claim 1, wherein the pre-freezing is carried out at -60 to -20 ° C before vacuum drying.
A sulfur-nitrogen co-doped graphene-based aerogel obtained by the production method according to any one of claims 1 to 8.
Use of a sulfur-nitrogen co-doped graphene-based aerogel according to claim 9 for oil-water separation.